Optical recording medium, recording, and reproduction apparatus having multiple recording capacity features

ABSTRACT

A recording and reproduction apparatus using a plurality of generations of optical recording media and an optical recording medium used in such a recording and reproduction apparatus, wherein the optical recording medium comprises first and second recording areas, the first recording area is divided into a plurality of zones, each of the plurality of zones is divided into a plurality of divided areas of one type among a plurality of types set in advance, the plurality of divided areas are assigned addresses and have fixed recording capacities, and identification information indicating the one type is recorded in the second recording area. The apparatus focuses a laser beam on the second recording area to read the identification information and records information on the first recording area or detects recorded information of the first recording area based on the identification information. The optical recording medium is for example a magneto-optical disk.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical recording medium such as anoptical disk and to a recording and reproduction apparatus for recordinginformation on an optical recording medium and detecting recordedinformation on an optical recording medium.

2. Description of the Related Art

In recent years, the recording densities of optical disks have beenimproved. Further, their formats, which determine the recording andreproduction systems, have been changed.

For example, in a 90 mm size magneto-optical disk (MO disk) of theInternational Organization for Standardization (ISO) standard, the firstgeneration capacity was 128 MB, the second generation capacity 230 MB,and the third generation capacity 640 MB. The recording capacity hasimproved with each generation.

Similarly, in a 130 mm size magneto-optical disk, the first generationcapacity was 650 MB, the second generation capacity 1.3 GB, and thethird generation capacity 2.0 GB. Again, the recording capacity hasimproved with each generation.

The size of a beam spot of a laser beam focused on an optical disk isdetermined by optical parameters such as the wavelength λ of the laserbeam used and the numerical aperture NA of the object lens, so theformat of an optical disk is closely related with the opticalparameters.

In the format of optical disks in the related art, the opticalparameters have been changed along with each generation to enablerecording and reproduction of finer marks using a smaller beam spot.

Also, the modulation and demodulation methods, addressing method, methodof division of recording regions, etc. have been changed so as to besuited for the finer marks. For example, the zone format, the number ofaddresses in a zone, the recording capacity of an address, modulationmethod, demodulation method, etc. have been changed with everygeneration. As a result, the recording capacity of optical disks hasbeen improved along with each generation.

Recording and reproduction apparatuses for third generation opticaldisks are designed based on these changes in first and second generationformats so as to be able to handle first, second, and third generationoptical disks.

Summarizing the problem to be solved by the invention, generally,however, recording and reproduction apparatus designed for firstgeneration optical disks cannot handle second and third generationoptical disks. This is because in the first generation, it was difficultto predict the modulation and demodulation methods, addressing methods,etc. of the following generations.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a recording andreproduction apparatus capable of using a plurality of generations ofoptical media.

Another object of the present invention is to provide an opticalrecording medium able to be used in such a recording and reproductionapparatus.

According to a first aspect of the present invention, there is providedan optical recording medium comprising first and second recording areas,wherein the first recording area being divided into a plurality ofzones; each of the plurality of zones being divided into a plurality ofdivided areas of one type among a plurality of N number of types (N isan integer more than 1) set in advance; the plurality of divided areasincluded in each of the plurality of zones being assigned addresses andhaving fixed recording capacities; and identification informationindicating the one type being recorded in the second recording area.

Preferably, the medium comprises a magneto-optical disk and at least oneof the first and second recording areas comprises an area in whichinformation is recorded by a magnetic field modulation recording systemand recorded information is reproduced by a reproduction system using adomain wall displacement phenomenon or a super resolution phenomenon.

Preferably. the second recording area is further recorded withconditional information indicating at least one of recording conditionsand reproduction conditions.

Alternatively, preferably the medium comprises an optical disk; thefirst recording area is an area positioned between a read-in area and aread-out area in the information area; and the second recording areacomprises at least one of the read-in area and the read-out area.

According to a second aspect of the present invention, there is providedan optical recording medium comprising first and second recording areas,wherein the first recording area is divided into a plurality of zones;each of the plurality of zones is divided into a fixed plurality ofdivided areas; the plurality of divided areas included in each of theplurality of zones have one type of recording capacity among recordingcapacities of M number of types (M is an integer more than 1) set inadvance and are assigned addresses; and identification informationindicating the one type is recorded in the second recording area.

Preferably, the medium comprises a magneto-optical disk and at least oneof the first and second recording areas comprises an area in whichinformation is recorded by a magnetic field modulation recording systemand recorded information is reproduced by a reproduction system using adomain wall displacement phenomenon or a super resolution phenomenon.

Preferably, the second recording area is further recorded withconditional information indicating at least one of recording conditionsand reproduction conditions.

Alternatively, preferably the medium comprises an optical disk; thefirst recording area comprises an area positioned between a read-in areaand a read-out area in the information area; and the second recordingarea comprises at least one of the read-in area and the read-out area.

According to a third aspect of the present invention, there is provideda recording and reproduction apparatus focusing a laser beam on anoptical recording medium to record information on the optical recordingmedium and detect recorded information of the optical recording medium,wherein the optical recording medium has first and second recordingareas, wherein the first recording area is divided into a plurality ofzones, each of the plurality of zones is divided into a plurality ofdivided areas of one type among a plurality of N number of types (N isan integer more than 1) set in advance, the plurality of divided areasincluded in each of the plurality of zones are assigned addresses andhave a fixed recording capacity, and identification informationindicating the one type is recorded in the second recording area; andthe apparatus focuses the laser beam on the second recording area toread the identification information and records information on the firstrecording area and detects recorded information of the first recordingarea based on the read identification information.

Preferably, the optical recording medium comprises a magneto-opticaldisk; and at least one of the first and second recording areas comprisesan area in which information is recorded by a magnetic field modulationrecording system and recorded information is reproduced by areproduction method using a domain wall displacement phenomenon or superresolution phenomenon.

Preferably, the second recording area is further recorded withconditional information indicating at least one of recording conditionsand reproduction conditions; and the apparatus focuses the laser beam onthe second recording area to read the identification information andconditional information and focuses a laser beam in accordance with theread identification information on the first recording area to recordinformation or detect recorded information of the first recording area.

Alternatively, preferably the optical recording medium comprises anoptical disk; the first recording area comprises an area positionedbetween a read-in area and a read-out area in the information area; andthe second recording area comprises at least one of the read-in area andthe read-out area.

According to a fourth aspect of the present invention, there is provideda recording and reproduction apparatus focusing a laser beam on anoptical recording medium to record information on the optical recordingmedium and detect recorded information of the optical recording medium,wherein the optical recording medium has first and second recordingareas, wherein the first recording area is divided into a plurality ofzones, each of the plurality of zones is divided into a fixed pluralityof divided areas, the plurality of divided areas included in each of theplurality of zones have one type of recording capacity among recordingcapacities of M number of types (M is an integer more than 1) set inadvance and are assigned addresses, and identification informationindicating the one type is recorded in the second recording area; andthe apparatus focuses the second recording area on the second recordingarea to read the identification information and records information onthe first recording area and detects recorded information of the firstrecording area based on the read identification information.

Preferably, the optical recording medium comprises a magneto-opticaldisk; and at least one of the first and second recording area comprisesan area in which information is recorded by a magnetic field modulationrecording system and recorded information is reproduced by areproduction system using a domain wall displacement phenomenon or superresolution phenomenon.

Preferably, the second recording area is further recorded withconditional information indicating at least one of recording conditionsand reproduction conditions; and the apparatus focuses the laser beam onthe second recording area to read the identification information andconditional information and focuses a laser beam in accordance with theread identification information on the first recording area to recordinformation on the first recording area and detect recorded informationof the first recording area.

Alternatively, the optical recording medium comprises an optical disk;the first recording area comprises an area positioned between a read-inarea and a read-out area in the information area; and the secondrecording area is at least one of the read-in area and the read-outarea.

That is, in the above first optical recording medium, since each of theplurality of zones included in the first recording area is divided intoa plurality of divided areas of one type among a plurality of N numberof types, each of the plurality of divided areas is assigned an address,and each has a fixed recording capacity, the recording density and/orrecording capacity can be improved by selecting a type having largerdivided areas from the N number of types.

In the first recording and reproduction apparatus, by focusing a laserbeam on the second recording area of the first optical recording mediumto read identification information of the above one type and recordinginformation or detecting recorded information in the first recordingarea based on the read identification information, it is possible to useoptical recording media of a plurality of generations having differentrecording densities and/or recording capacities.

In the above second optical recording medium, since each of theplurality of zones included in the first recording area is divided intoa fixed plurality of divided areas, each of the plurality of dividedareas has a recording capacity of one type among the recordingcapacities of M number of types, and each is assigned an address, therecording density and/or recording capacity can be improved by selectinga type having larger divided areas from the M number of types.

In the second recording and reproduction apparatus, by focusing a laserbeam on the second recording area on the second optical recording mediumto read identification information of the above one type and recordinginformation or detecting recorded information in the first recordingarea based on the read identification information, it is possible to useoptical recording media of a plurality of generations having differentrecording densities and/or recording capacities.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention willbecome clearer from the following description of the preferredembodiments given with reference to the accompanying drawings, in which:

FIG. 1 is a schematic explanatory view of the relationship of arecording and reproduction apparatus and an optical disk according tothe present invention;

FIG. 2 is a view for explaining a magnetic field modulation recordingsystem;

FIG. 3 is an explanatory view of how a record mark is formed on amagneto-optical disk by the magnetic field modulation recording system;

FIGS. 4A and 4B are views for explaining an example of a reproductionsystem using domain wall displacement;

FIG. 5 is a graph of the characteristics of two types of magneto-opticaldisks for recording a signal by the magnetic field modulation recordingsystem and for reproducing a signal by a reproduction system usingdomain wall displacement;

FIGS. 6A to 6D are views for explaining the difference between two typesof magneto-optical disks;

FIG. 7 is a view for explaining the structure of the format of anoptical disk according to the present invention;

FIG. 8 is a view for explaining a data table defining numbers ofaddresses in a zone by type;

FIG. 9 is a view for explaining a data table defining recordingcapacities of divided areas corresponding to addresses in a zone bytype;

FIG. 10 is a schematic view of the block configuration of a recordingand reproduction apparatus according to an embodiment of the presentinvention;

FIG. 11 is a schematic view of the configuration of an optical pickup ofthe recording and reproduction apparatus of FIG. 10; and

FIG. 12 is an explanatory view of the configuration of a light receivingportion of an optical detector of the optical pickup of FIG. 11.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Below, preferred embodiments will be described with reference to theaccompanying drawings.

FIG. 1 is a schematic view for explaining the relationship between arecording and reproduction apparatus and an optical disk according tothe present invention.

The recording and reproduction apparatus 190 comprises an optical systemwhich records information on an optical recording medium and detectsrecorded information on the optical recording medium by focusing a laserbeam on an optical disk 81 a or 81 b.

The recording and reproduction apparatus 190 can use a Q-generationoptical disk 81 a of type 1 and a (Q+1) generation optical disk 81 b oftype 2, where Q is a natural number. The optical disks 81 a and 81 b areimproved in recording capacity in the order of type 1 and type 2.

The optical disks 81 a and 81 b have substantially the same externalform, track shape, and address shape and have servo signals, addresssignals, and reproduction signals which can be detected by using theoptical system. The optical disks 81 a and 81 b may also be insertedinto cartridges and the cartridges mounted in the recording andreproduction apparatus 190.

Next, the principle of improvement of the recording capacity of anoptical disk with the same optical parameters will be explained as anexample. As an optical disk, a magneto-optical disk is used as anexample.

The magnetic field modulation recording system is a recording systemcapable of recording marks smaller than a size of a beam spot of a laserbeam on a recording layer of a magneto-optical disk.

FIGS. 2 and 3 are views for explaining the magnetic field modulationrecording system.

In FIG. 2, an object lens 2 and a magnetic head 20 are arranged facingto each other across a magneto-optical disk 81.

At the time of recording, a record mark is formed by forming a beam spotof a laser beam LB on the recording layer in the magneto-optical disk 81by the object lens 2 and alternating the direction of the magnetic fieldof the magnetic line of force generated by the magnetic head 20.

FIG. 3 is a view of how a record mark is formed on the magneto-opticaldisk 81 by the magnetic field modulation system.

The recording layer of the magneto-optical disk 81 is formed with atrack Tr and guides GD of the track Tr. A beam spot BS of the laser beamLB is focused on the recording layer. The center of the beam spot ispositioned at the center portion of the track Tr. For example, the trackTr may be made a groove and the guides GD made lands. Alternatively, thetrack Tr may be made a land and the guides GD made grooves.

A high temperature portion HT of the beam spot BS is a region exceedingthe Curie temperature of the recording layer. Outside the hightemperature portion HT, the temperature becomes lower than the Curietemperature. The high temperature portion HT is magnetized by anexternal magnetic field from the magnetic head 20. A record mark MKbecomes a chevron shape or a crescent shape corresponding to thetemperature gradient formed by the high temperature portion HT of thebeam spot BS.

Accordingly, by alternating the external magnetic field, as illustrated,record marks MK smaller than the beam spot BS can be successively formedin the track direction.

In this way, by using the magnetic field modulation recording system,recording at a higher density becomes possible without making the beamspot BS smaller.

Next, an example of a reproduction system capable of reproducinginformation recorded at a high density without making the beam spotsmaller will be explained.

Japanese Unexamined Patent Publication (Kokai) No. 6-290496 disclosessuch a magneto-optical reproduction method.

In this magneto-optical reproduction method, the magneto-optical diskcomprises at least a three-layer magnetic film including a displacementlayer, switching layer, and memory layer. When reproducing a signal, thesize of the recorded magnetic domain is substantially enlarged toincrease the reproduction carrier signal by using domain walldisplacement of the displacement layer in a region where the temperatureof the magnetic layer becomes equal to or higher than the Curietemperature of the switching layer.

This reproduction system using domain wall displacement is called domainwall displacement detection (DWDD). This reproduction system will beexplained with reference to FIGS. 4A and 4B.

FIG. 4A is a view of how a laser beam LB is focused on a displacementlayer 81T, switching layer 81S, and memory layer 81M. Note that thethree-layer magnetic film comprised of the displacement layer 81T,switching layer 81S, and memory layer 81M corresponds to a recordinglayer.

The memory layer 81M is recorded with a signal (or information) inaccordance with the length of the magnetic domain Y having a spinpolarization SP (magnetization direction). The interface betweenadjacent magnetic domains 81Y is a domain wall 81W.

During signal reproduction, when the recording layer is locally heatedby the laser beam LB, a temperature gradient as shown in FIG. 4B isformed.

In the switching layer 81S, a region where the temperature is higherthan the Curie temperature of the switching layer 81S is demagnetizedand cut in exchange coupling with the memory layer 81M. Further, onlythe domain wall 81W in the displacement layer 81T having a small domainwall magneto restrictive force displaces to the high temperature side.

Every time a domain wall 81W, formed at intervals in accordance with asignal recorded on the memory layer 81M, reaches an isotherm of theCurie temperature along with rotation of the magneto-optical disk 81,domain wall displacement occurs in the displacement layer 81T and spinpolarization SP of the magnetic domain 81Y enlarged by the domain walldisplacement is detected, whereby a recording signal can be detected.

The DWDD system has the advantage that a large signal can be taken outfrom fine recording magnetic domains 81Y having a smaller period than alimit of optical resolution of the laser beam LB and thereforeinformation recorded at a high density can be detected without changingoptical parameters such as the wavelength λ of the laser beam andnumerical aperture NA of the object lens.

In the magneto-optical reproduction system, as a system using the abovemagnetic domain enlarging phenomenon, there is the system of enlargingthe recording magnetic domains by a reproduction magnetic field from theoutside (magnetic amplifying magneto-optical system, so-called MAMMOS).Further, there is a super resolution system using the high temperatureportion at the center of the beam spot (so-called “center aperturedetection” (CAD) in magnetically induced super resolution (MSR)). Theseare capable of attaining a high density without changing the opticalparameters, so are promising systems for further increasing therecording density.

FIG. 5 is a graph of the characteristics of two types of magneto-opticaldisks for recording a signal by the magnetic field modulation recordingsystem and reproducing the signal by the DWDD system. Here, the casewhere the optical disks 81 a and 81 b are magneto-optical disks and havethe illustrated characteristic curves Ka and Kb will be explained as anexample.

In FIG. 5, the abscissa indicates a linear recording density, while theordinate indicates a power margin of a laser beam at the time ofrecording and reproduction.

The linear recording density indicates a limit density capable ofsecuring a predetermined error rate. The track pitches are the same, andthe changes in the recording density are formed by changes of recordingdensity in the track direction.

On the other hand, the power margin indicates the range of fluctuationof the laser power enabling normal recording and reproduction. Thelarger the power margin is, the greater the resistance to temperaturechanges and aging and the more possible it is to deal with manufacturingvariations in magneto-optical disks and recording and reproductionapparatuses.

The power margin also arises due to dispersion of a beam spot caused bypoor focusing and inclination of the laser beam and has a bearing on thedegree of allowance of such fluctuations.

In the chart of FIG. 5, the characteristics curves Ka and Kb of themagneto-optical disks 81 a and 81 b indicate that the higher therecording density, the less the power margin. Also, under the same powermargin, the magneto-optical disk 81 b can give a higher recordingdensity compared with the magneto-optical disk 81 a.

In the recording and reproduction apparatus 190, generally a certainpower margin has to be secured. For example, when a power margin P isrequired, the recording density B becomes the limit in themagneto-optical disk 81 b and the recording density A becomes the limitin the magneto-optical disk 81 a.

FIGS. 6A to 6D are views for explaining the difference between themagneto-optical disks 81 a and 81 b.

FIG. 6A is an enlarged view for explaining a track of themagneto-optical disk 81 b, while FIG. 6B is an enlarged view forexplaining the magneto-optical disk B1 b.

FIG. 6C is an enlarged view for explaining a track of themagneto-optical disk 81 a, while FIG. 6D is an enlarged view forexplaining the magneto-optical disk 81 a.

In the magneto-optical disks 81 a and 81 b shown in FIGS. 6A to 6D, arecording layer 81Q is formed on a disk substrate 81P. Lands and groovesare formed by the topology of the recording layer 81Q. The groovescorrespond to the tracks Tr, while the lands correspond to the guidesGD0 and GD1.

The magneto-optical disk 81 b shown in FIGS. 6A and 6B is formed byfiring a laser beam having a short wavelength at a high power on theguide GD0 of a track interface of the magneto-optical disk 81 a shown inFIGS. 6C and 6D to convert it to the guide GD1 and burning apart therecording layer of the track interface of the magneto-optical disk 81 ato form a cut region 81R. By adopting this configuration, the magneticconnection between adjacent tracks is cut and displacement of the domainwalls becomes smooth, so fine marks (or a signal) can be reproducedstably.

Note that the magneto-optical disk 81 b becomes higher in cost comparedwith the magneto-optical disk 81 a since the lands are burnt apart by ahigh power laser beam.

As another method for improving the recording density, there is themethod of irradiating a track with ultraviolet rays for annealing itbefore recording the signal. The annealing can make the displacement ofthe domain walls smooth. Note that this method is also higher in costcompared with an magneto-optical disk which is not annealed since it isannealed by ultraviolet rays.

In view of the balance of costs and the recording density, it ispreferable to be able to record and reproduce on and from at least twotypes of magneto-optical disks. In the present embodiment, the format ofthe magneto-optical disk is defined as indicated below anticipating animprovement of the recording density.

FIG. 7 is a view for explaining the structure of the format of anoptical disk according to the present invention. The explanation will begiven describing the above magneto-optical disks 81 a and 81 b given asexamples of optical disks as the magneto-optical disk 81.

The magneto-optical disk 81 is formed with a center hole 83. A clampingarea 84 is used for holding the magneto-optical disk 81 on a turntablein the recording and reproduction apparatus 190.

The magneto-optical disk 81 comprises an information area 88. Theinformation area 88 is comprised of a first and second recording areas.

The first recording area is positioned between a read-in area 85 and aread-out area 86, is divided into a plurality of zones 82, and records avariety of information.

Each of the plurality of zones 82 is, as an example, divided to aplurality of divided areas of one type among a plurality of apredetermined N number of types (N is an integer more than 1). Also,each of the plurality of divided areas included in the respective zonesis assigned an address and has a fixed recording capacity.

Note that in the explanatory view of FIG. 7, 12 address areas 87positioned in the inner-most zone are shown as an example, and theaddress areas in other zones are omitted.

The second recording area comprises a read-in area 85 on an innercircumference side and a read-out area 86 on an outer circumferenceside, records identification information showing the one type, andrecords information indicating the difference of the recording densityfrom the first recording area.

The magneto-optical disk 81 mounted on the turntable of the recordingand reproduction apparatus 190 is made to rotate at a predeterminedrotational speed (for example, a constant linear velocity) in accordancewith the area or zone 82 on which the beam spot BS is focused.

An address signal of the address area 87 is composed of topologicalmarks called “emboss pits”. The recording and reproduction positions ofa signal are set in accordance with the address. Note that the dividedarea corresponding to an address area 87 may also be made a sector.

In the magneto-optical disk 81, the difference of the recording densityis defined by the identification information of the type. The recordingcapacity of the zones 82 is changed in accordance with theidentification information.

A first method of changing the recording capacity of the zones 82 is tomake the recording capacities of the divided areas (for example sectors)constant and to define the number of addresses in the zones by type.

FIG. 8 illustrates the first method and is an explanatory view of a datatable defining the number of addresses in zones by type. The zonepositioned at the inner-most circumference is designated zone no. 1,while the zones outward from there are designated zone no. 2, zone no.3, etc. The radial position of each zone and the number of sectoraddresses per track (one turn of the track) are defined by type.

Zone no. 1 is positioned at a radius of 22.6 mm to 25.4 mm, has 4000tracks, and has 20 addresses per track in type 1 and 25 in type 2.

Zone no. 2 is positioned at a radius of 25.4 mm to 28.2 mm, has 4000tracks, and has 22 addresses per track in type 1 and 27 in type 2.

Zone no. 3 is positioned at a radius of 28.2 mm to 31.0 mm, has 4000tracks, and has 24 addresses per track in type 1 and 30 in type 2.

The recording density can be improved in the order of type 1 and type 2in this way.

A second method of changing the recording capacity of the zones 82 is tomake the number of addresses constant in the zones and to define therecording capacity of divided areas corresponding to the addresses(recording capacity per address) by type.

FIG. 9 illustrates the second method and is an explanatory view of adata table defining the recording capacity of the divided areascorresponding to addresses in the zones. The zone positioned at theinner-most circumference is designated zone no. 1, while the zonesoutward from there are designated zone no. 2, zone no. 3, etc. Theradial position of each zone and the number of sector addresses pertrack are defined by type.

Zone no. 1 is positioned at a radius of 22.6 mm to 25.4 mm, has 4000tracks, and has 25 addresses per track. The recording capacity peraddress is 4 kB in type 1 and 5 kB in type 2.

Zone no. 2 is positioned at a radius of 25.4 mm to 28.2 mm, has 4000tracks, and has 27 addresses per track. The recording capacity peraddress is 4 kB in type 1 and 5 kB in type 2.

Zone no. 3 is positioned at a radius of 28.2 mm to 31.0 mm, has 4000tracks, and has 29 addresses per track. The recording capacity peraddress is 4 kB in type 1 and 5 kB in type 2.

The recording density can be improved in the order of type 1 and type 2in this way.

The recording and reproduction apparatus 190 for the above recordingformat first detects the identification information in the read-in areaor read-out area before recording and reproducing the signal. At thetime of recording and reproduction, it accesses a desired sector addressby referring to the above data table, obtaining a position of an aimedzone in accordance with the detected type, and reading an address signalof emboss pits.

Also, the recording and reproduction apparatus 190 can store apredetermined data table in an internal memory in a control circuit forreference as needed.

To secure the interchangeability of the different types ofmagneto-optical disks 81 (magneto-optical disks 81 a and 81 b),conditional information indicating the recording conditions and/orreproduction conditions of the magneto-optical disk 81 may be recordedin the second recording area of the magneto-optical disk 81. Therecording conditions are, for example, the laser power, duty factor ofthe laser beam LB, intensity of the recording magnetic field, etc.

In the magneto-optical disk 81, by using the magnetic field modulationrecording system and a reproduction system using the magnetic domainenlarging phenomenon or super resolution phenomenon, the recordingdensity can be increased without changing optical parameters. Further, arecording and reproduction apparatus for current generationmagneto-optical disks can handle next generation magneto-optical diskshaving an increased recording capacity.

FIG. 10 is a schematic view of the configuration of arecording/recording apparatus according to an embodiment of the presentinvention.

The recording and reproduction apparatus 190 focuses the laser beam LBon the second recording area of the magneto-optical disk 81 to read theidentification information and the conditional information, focuses thelaser beam LB in accordance with the read conditional information on thefirst recording area to record information on the first recording area,or focuses the laser beam in accordance with the conditional informationon the first recording area to detect recorded information in the firstrecording area.

The recording and reproduction apparatus 190 comprises a modulationcircuit 10, a magnetic head 20, a magnetic head drive circuit 25, amotor 30, a motor drive circuit 35, a phase compensation circuit 40, anamplifying circuit 42, an optical pickup 150, an amplifying circuit(head amplifier) 152, a laser drive circuit 155, a generation circuit160, an information detection circuit 165, a control circuit 170, and arecording/reproduction switching circuit 175.

The recording and reproduction apparatus 190 records information on therotating magneto-optical disk 81 or detects recorded information fromthe rotating magneto-optical disk 81.

The control circuit 170 is a controller for controlling the recordingand reproduction apparatus 190 as a whole and is comprised for exampleby a microcomputer.

The control circuit 170 controls the motor drive circuit 35, the laserdrive circuit 155, the optical pickup 150, the phase compensationcircuit 40, the generation circuit 160, the information detectioncircuit 165, the magnetic head drive circuit 25, the modulation circuit10, etc. Also, the control circuit 170 comprises an internal memorystoring the data tables shown in FIG. 8 and 9.

The optical pickup 150 focuses the laser beam LB on a recording positionof the magneto-optical disk 81 at the time of recording and focuses thelaser beam LB on the reproducing position of the magneto-optical disk 81at the time of reproduction. Note that the power of the laser beam LB islarger at recording than reproduction.

The modulation circuit 10 receives as input an input signal Sinindicating information to be recorded at recording, modulates the inputsignal Sin by eight-to-fourteen modulation (EFM) etc. to generate anoutput signal S10, and supplies the output signal S10 to the magnetichead drive circuit 25.

The magnetic head drive circuit 25 supplies an excitation current S25for driving use to the magnetic head 20 based on the output signal S10of the modulation circuit 10.

The magnetic head 20 is excited at its core by the excitation currentS25 from the magnetic head drive circuit 25, generates a magnetic lineof force MB in accordance with the input signal Sin from the core, andapplies a magnetic field in accordance with the input signal Sin to theportion of the magneto-optical disk 81 where the beam is focused.

The motor 30 is for example comprised of a spindle motor and rotates themagneto-optical disk 81 at a predetermined rotational speed. The motor30 rotates the magneto-optical disk 81, for example, so that the linearvelocity becomes constant.

The motor drive circuit 35 drives the motor 30 by supplying a drivecurrent to the motor 30. The motor drive circuit 35 may control therotation of the motor 30 by pulse width modulation (PWM) or phase lockedloop (PLL) control.

The laser drive circuit 155 generates a drive signal SL under thecontrol of the control circuit 170, drives a semiconductor laser in theoptical pickup by the drive signal SL, and causes a laser beam LB to beoutput from the semiconductor laser.

The optical pickup 150 supplies the laser beam LB to a track of themagneto-optical disk 81 and focuses it on the recording position orreproducing position of the magneto-optical disk 81.

At the time of recording, the focused portion of the magneto-opticaldisk 81 becomes a high temperature exceeding the Curie temperature ofthe recording layer, the focused portion is magnetized by the magneticfield applied by the magnetic head 20, and therefore the input signalSin is recorded.

The amplifying circuit (head amplifier) 152 amplitudes output signals SAto SF of an optical detector in the optical pickup 150 and supplies themto the generation circuit 160.

The generation circuit 160, based on the output signals SA to SF of theoptical detector from the amplifying circuit 152, generates areproduction signal RF corresponding to the amount of light (amount ofreflected light) of the reflected laser beam, a reproduction signal MObased on a magneto-optical signal, a focus error signal FE, and atracking error signal TE.

The phase compensation circuit 40 performs compensation (phasecompensation and/or frequency compensation) on the focal error signal FEand the tracking error signal TE to generate compensated signals andsupplies the compensated signals to the amplifying circuit 42.

The amplifying circuit 42 amplifies the compensated signal of the focuserror signal FE to generate a drive signal Sfe and supplies the same toa focusing actuator in the optical pickup 150.

Also, the amplifying circuit 42 amplifies the compensated signal of thetracking error signal TE to generate a drive signal Ste and supplies thesame to the tracking actuator in the optical pickup 150.

The information detection circuit 165 receives the reproduction signalMO from the generation circuit 160, demodulates the reproduction signalMO to detect recorded information of the magneto-optical disk 81, andoutputs the detected recorded signal as an output signal So.

The recording/reproduction switching circuit 175 generates a switchingsignal for switching between recording and reproduction of the recordingand reproduction apparatus 190 and supplies the switching signal to thecontrol circuit 170, the information detection circuit 165, themodulation circuit 10, magnetic head drive circuit 25, etc.

The modulation circuit 10 stops supplying the output signal S10 to themagnetic head drive circuit 25 when the switching signal indicatingreproduction is supplied. Also, the magnetic head drive circuit 25 stopssupplying the excitation current S25 to the magnetic head 20 when theswitching signal indicating reproduction is supplied.

On the other hand, the information detection circuit 165 stopsgenerating the output signal So when the switching signal indicatingrecording is supplied.

The control circuit 170 controls the laser output power of the opticalpickup 150 in accordance with the switching signal or detectsidentification information and conditional information from thereproduction signal RF to control the laser output power and/or dutyfactor based on the conditional information and control the size of themagnetic line of force MB generated by the magnetic head 20.

Furthermore, the control circuit 170 detects an address from thereproduction signal RF and controls the recording and reproductionapparatus 190 to record information based on the detected address,identification information, and data table and to detect recordedinformation based on the detected address, identification information,and data table.

FIG. 11 is a schematic view of the configuration of the optical pickup150 included in the recording and reproduction apparatus 190.

The optical pickup 150 comprises a semiconductor laser 4, collimatorlens 5, beam splitter 3, object lens 2, condenser lens 6, cylindricallens 7, optical detector 18, lens holder 2H, focusing actuator 2F,tracking actuator 2T, and Wollaston prism 15.

The object lens 2 is held by the lens holder 2H.

The focusing actuator 2F, based on the drive signal Sfe, moves the lensholder 2H in a direction perpendicular to a recording surface of themagneto-optical disk 81 so as to move the object lens 2 in the focaldirection.

The tracking actuator 2T, based on the drive signal Ste, moves the lensholder in the radial direction of the magneto-optical disk 81 so as tomove the object lens 2 in the radial direction of the magneto-opticaldisk 81.

The semiconductor laser 4 outputs a linear polarized laser beam andsupplies the same to the collimator lens 4 based on the drive signal SL.

The collimator lens 5 converts the laser beam from the semiconductorlaser 4 to parallel light and supplies the same to the beam splitter 3.

The beam splitter 3 passes the laser beam from the collimator lens 5 tosupply it to the object lens 2.

The object lens 2 focuses the laser beam from the beam splitter 3 andsupplies it to a track of the magneto-optical disk 81 having landsand/or grooves.

Also, the object lens 2 returns the laser beam reflected on themagneto-optical disk 81 to the beam splitter 3.

The beam splitter 3 is struck by the laser beam from the object lens 2,reflects and emits the incident laser beam, and supplies it to theWollaston prism 15.

The Wollaston prism 15 separates the laser beam from the beam splitter 3to a main beam and first and second sub beams and supplies them to thecondenser lens 6.

The condenser lens 6 condenses the laser beams from the Wollaston prism15 and supplies them to the cylindrical lens 7.

The cylindrical lens 7 passes the laser beams from the condenser lens 6and supplies them to the optical detector 18.

The optical detector 18 receives the laser beams from the cylindricallens 7 at a light receiving portion and generates output signals SA toSF.

FIG. 12 is a view for explaining the configuration of the lightreceiving portion of the optical detector 18. The light receivingportion of the optical detector 18 comprises a main light receivingportion 18S, a first sub light receiving portion 18E, and a second sublight receiving portion 18F.

The main light receiving portion 18S is supplied with the main beam fromthe Wollaston prism 15 via the condenser lens and the cylindrical lens7. The main light receiving portion 18S is divided into quarters by twodividing lines 18Sx and 18Sy and therefore has four divided regions 18Ato 18D. At the light receiving portion 18S in FIG. 12 is formed a beamspot MS by the main beam from the cylindrical lens 7.

The symmetry axis of the cylindrical lens 7 forms an angle of about 45°or about 135° with the direction of the dividing line 18Sx or 18Sy ofthe main light receiving portion 18S.

The intersection of the dividing lines 18Sx and 18Sy is positioned atthe center or substantial center of the main beam passed through thecylindrical lens 7.

The shape of the beam spot MS formed on the main light receiving portion18S changes in the diagonal direction in accordance with the distancebetween the magneto-optical disk 81 and the object lens 2, so poor focuson the magneto-optical disk 81 can be detected by the astigmatism methodbased on the output signals SA to SD generated by the divided regions18A to 18D. Also, tracking error can be detected by the push-pull methodetc.

The first sub light receiving portion 18E is supplied with the first subbeam separated by the Wollaston prism 15 via the condenser lens 6 andthe cylindrical lens 7 and generates an output signal SE. On the firstsub light receiving portion 18E in FIG. 12 is formed a beam spot SSE bythe first sub beam from the cylindrical lens 7.

The second sub light receiving portion 18F is supplied with the secondsub beam separated by the Wollaston prism 15 via the condenser lens 6and the cylindrical lens 7 and generates an output signal SF. On the sublight receiving portion 18F is formed a beam spot SSF by the second subbeam from the cylindrical lens 7.

The generation circuit 160 in the recording and reproduction apparatus190, for example, generates a reproduction signal MO as amagneto-optical signal based on the difference of the above outputsignals SE and SF (SE−SF) from the amplifying circuit 152. Also, thegeneration circuit 160 generates a focal error signal FE using the aboveoutput signals SA to SD from the amplifying circuit 152 based on(SA+SC−SB−SD), generates a tracking error signal TE based on(SA+SD−SB−SC), and generates a reproduction signal RF in accordance withthe amount of light (amount of reflected light) based on (SA+SB+SC+SD).

Note that the above embodiments were described as examples of thepresent invention and that the present invention is not limited to theabove embodiments.

Summarizing the effects of the invention, in the above first opticalrecording medium, each of the plurality of zones included in the firstrecording area is divided into a plurality of divided areas of one typeamong a plurality of N number of types, each of the plurality of dividedareas is assigned an address, and each has a fixed recording capacity,so the recording density and/or recording capacity can be improved byselecting a type having larger divided areas from the N number of types.

In the first recording and reproduction apparatus, by focusing a laserbeam on the second recording area of the first optical recording mediumto read identification information of the above one type and recordinginformation or detecting recorded information in the first recordingarea based on the read identification information, it is possible to useoptical recording media of a plurality of generations having differentrecording densities and/or recording capacities.

In the above second optical recording medium, each of the plurality ofzones included in the first recording area is divided into a fixedplurality of divided areas, each of the plurality of divided areas has arecording capacity of one type among the recording capacities of Mnumber of types, and each is assigned an address, so the recordingdensity and/or recording capacity can be improved by selecting a typehaving larger divided areas from the M number of types.

In the second recording and reproduction apparatus, by focusing a laserbeam on the second recording area on the second optical recording mediumto read identification information of the above one type and recordinginformation or detecting recorded information in the first recordingarea based on the read identification information, it is possible to useoptical recording media of a plurality of generations having differentrecording densities and/or recording capacities.

1-4. (canceled)
 5. An optical recording medium comprising first andsecond recording areas, wherein: said first recording area is dividedinto a plurality of zones; each of said plurality of zones is dividedinto a fixed plurality of divided areas; said plurality of divided areasincluded in each of said plurality of zones have one recording capacityamong M number of recording capacities (M is an integer more than 1) setin advance and are assigned addresses; and identification informationindicating said one recording capacity is recorded in said secondrecording area; wherein said second recording area including recordsinformation indicating a difference in recording density from the firstrecording area. 6-16. (canceled)